['Air Programs']
['Air Emissions']
03/16/2023
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Use the following special provisions for testing snowmobiles:
(a) You may perform steady-state testing with either discrete-mode or ramped-modal cycles. You must use the type of testing you select in your application for certification for all testing you perform for that engine family. If we test your engines to confirm that they meet emission standards, we will do testing the same way. If you submit certification test data collected with both discrete-mode and ramped-modal testing (either in your original application or in an amendment to your application), either method may be used for subsequent testing. We may also perform other testing as allowed by the Clean Air Act. Measure steady-state emissions as follows:
(1) For discrete-mode testing, sample emissions separately for each mode, then calculate an average emission level for the whole cycle using the weighting factors specified for each mode. In each mode, operate the engine for at least 5 minutes, then sample emissions for at least 1 minute. Calculate cycle statistics and compare with the established criteria as specified in 40 CFR 1065.514 to confirm that the test is valid.
(2) For ramped-modal testing, start sampling at the beginning of the first mode and continue sampling until the end of the last mode. Calculate emissions and cycle statistics the same as for transient testing as specified in 40 CFR part 1065, subpart G.
(3) Measure emissions by testing the engine on a dynamometer with one or more of the following sets of duty cycles to determine whether it meets the steady-state emission standards in §1051.103:
(i) The following duty cycle applies for discrete-mode testing:
| Mode No. | Speed (percent) 1 | Torque (percent) 2 | Minimum time in mode (minutes) | Weighting factors |
|---|---|---|---|---|
| 1 | 100 | 100 | 3.0 | 0.12 |
| 2 | 85 | 51 | 3.0 | 0.27 |
| 3 | 75 | 33 | 3.0 | 0.25 |
| 4 | 65 | 19 | 3.0 | 0.31 |
| 5 | Idle | 0 | 3.0 | 0.05 |
| 1 Percent speed is percent of maximum test speed. 2 Percent torque is percent of maximum torque at maximum test speed. | ||||
(ii) The following duty cycle applies for ramped-modal testing:
| RMC mode | Time in mode | Speed (percent) 1 | Torque (percent) 2 3 |
|---|---|---|---|
| 1a Steady-state | 27 | Warm Idle | 0 |
| 1b Transition | 20 | Linear Transition | Linear Transition |
| 2a Steady-state | 121 | 100 | 100 |
| 2b Transition | 20 | Linear Transition | Linear Transition |
| 3a Steady-state | 347 | 65 | 19 |
| 3b Transition | 20 | Linear Transition | Linear Transition |
| 4a Steady-state | 305 | 85 | 51 |
| 4b Transition | 20 | Linear Transition | Linear Transition |
| 5a Steady-state | 272 | 75 | 33 |
| 5b Transition | 20 | Linear Transition | Linear Transition |
| 6 Steady-state | 28 | Warm Idle | 0 |
| 1 Percent speed is percent of maximum test speed. 2 Advance from one mode to the next within a 20-second transition phase. During the transition phase, command a linear progression from the torque setting of the current mode to the torque setting of the next mode. 3 Percent torque is percent of maximum torque at maximum test speed. | |||
(b) During idle mode, operate the engine at its warm idle speed as described in 40 CFR 1065.510.
(c) For the full-load operating mode, operate the engine at wide-open throttle.
(d) Ambient temperatures during testing must be between 20°C and 30°C (68°F and 86°F), or other representative test temperatures, as specified in paragraph (f) of this section.
(e) See 40 CFR part 1065 for detailed specifications of tolerances and calculations.
(f) You may test snowmobiles at ambient temperatures below 20°C or using intake air temperatures below 20°C if you show that such testing complies with 40 CFR 1065.10(c)(1). You must get our approval before you begin the emission testing. For example, the following approach would be appropriate to show that such testing complies with 40 CFR 1065.10(c)(1):
(1) Using good engineering judgment, instrument a representative snowmobile built with a representative engine from the family being tested with an appropriate temperature measuring device located in the intake air plenum where fuel spitback is not likely to occur.
(2) Choose a time and location with the following weather conditions: windspeed less than 10 knots, no falling precipitation, air temperature between −20°C and 0°C (−4°F and 32°F).
(3) Operate the snowmobile until its engine reaches a steady operating temperature.
(4) Operate the snowmobile on a level surface free of other vehicle traffic. Operate the snowmobile at each specified engine speed corresponding to each mode in the emissions test specific to the engine being tested. When readings are stable, record the temperature in the intake air plenum and the ambient temperature. Calculate the temperature difference between the air in the plenum and the ambient air for each mode.
(5) Calculate the nominal intake air test temperature for each test mode as −10°C (14°F) plus the temperature difference for the corresponding mode determined in paragraph (f)(4) of this section.
(6) Before the emissions test, select the appropriate carburetor jetting for −10°C (14°F) conditions according to the jet chart. For each mode, maintain the inlet air temperature within 5°C (9°F) of the corresponding modal temperature calculated in paragraph (f)(5) of this section.
(7) Adjust other operating parameters to be consistent with operation at −10°C (14°F). For example, this may require that you modify the engine cooling system used in the laboratory to make its performance representative of cold-temperature operation.
[67 FR 68347, Nov. 8, 2002, as amended at 70 FR 40500, July 13, 2005; 73 FR 59253, Oct. 8, 2008]
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